Structure of rotor for outer rotor type brushless motor

ABSTRACT

The present invention relates to a structure of a rotor for a brushless motor which can improve structural stiffness, restrict noise generation by reducing vibration during the rotation, use cheap materials, reduce a fabrication cost by fabricating a back yoke and a base plate unit in a single body. improve durability, and efficiently cool a heat generated in the motor during the operation by facilitating an external air inflow. The structure of the rotor for the brushless motor includes: a steel plate frame provided with a base plate unit in a disc shape having a plurality of insertion holes at its center portion, a plurality of radiation holes being formed at a circumferential portion of the insertion holes, a plurality of blades being formed at side portions of the radiation holes by cutting: a back yoke unit curved and extended in the upward direction, having a predetermined height at the circumferential portion of the base plate unit; and a radius-direction enhancing unit formed at the upper end portion of the back yoke unit; one or a plurality of ring type permanent magnets fixedly connected to the inner side portion of the back yoke unit; a connecting member inserted into the insertion hole positioned at the center, and connected to the steel plate frame; and a fixing unit fixing a driving shaft inserted into the connecting member and connected to the other constitutional elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure of a rotor for an outerrotor type brushless motor (BLDC), and in particular to a structure of arotor for an outer rotor type brushless motor (BLDC) which can improvestructural stiffness, restrict noise generation by reducing vibrationduring the rotation, efficiently cool a heat generated in the motor,decrease a fabrication cost and improve durability.

2. Description of the Background Art

As illustrated in FIG. 1, a general outer rotor type brushless motor(BLDC) includes: a stator 100 where a coil is wound round a magneticcore 10; a resin frame 220 in a predetermined shape fabricated with aresin by using a die; a rotor 200 positioned outside the stator 100 inorder to be alternately rotated in the right and left directions; and asensor unit 300 connected to the stator 100, detecting a position of apermanent magnet 210 of the rotated rotor 200. and sequentiallytransmitting a current to the stator 100.

A driving shaft 400 is inserted into a center portion of the rotor 200.

The structure of the rotor 200 will now be described in more detail.

As depicted in FIGS. 2a and 2b, in the conventional outer rotor typebrushless motor, the resin frame 220 forming an outer shape of the rotor200 is formed having a predetermined height, a permanent magnetsupporting unit 222 connected with the permanent magnet 210 beingvertically curved and extended in an upward direction, and curved towardthe center portion, at the outer circumferential portion to adisc-shaped base unit 221.

A ring-shaped deposition groove 223 having a predetermined height andwidth is formed at the inner wail of the permanent magnet supportingunit 222. A ring-shaped back yoke 230 having a predetermined width isinserted into the deposition groove 223. The plurality of permanentmagnets 210 are stacked and adhered to the inner side portion of theback yoke 230 at predetermined intervals in a circumference direction.

The back yoke 230 is fabricated by rolling a thin steel plate. andserves to form a magnetic circuit of the permanent magnet 210. The backyoke 230 and the permanent magnet 210 are formed in a single body by athermoplastic resin.

On the other hand, a boss unit 224 having a predetermined height isformed at the center portion of the base unit 221. A through hole 224ais formed at the center portion of the boss unit 224. A serration unit225 having a plurality of triangle-shaped teeth is formed at the innercircumferential surface of the through hole 224a.

A shaft serration unit 401 formed at the outer circumferential surfaceof the driving shaft 400 is inserted into the serration unit 225 of theresin frame 220, and thus the resin frame 220 and the driving shaft 400are combined. A spacer 410 is inserted into the lower portion of theshaft serration unit 401 inserted into the serration unit 225 of theresin frame 220. A nut 420 is fastened to a lower portion of the spacer410, namely an end portion of the driving shaft 400.

On the other hand, a radiation fan blade 226 and a radiation hole 227are provided on the bottom surface of the base unit 221 in order to coola heat which is always generated during the rotation of the rotor 200 bymeans of an external air inflow.

As shown in FIG. 2b, a plurality of radiation blades 226 are formed inthe base unit 221 in a radial shape centering around the boss unit 224.The plurality of radiation blades 226 have a predetermined thickness andwidth, and are formed in a vertical direction from the boss unit 224 tothe permanent magnetic supporting unit 222.

In addition, a plurality of radiation holes 227 are formed in the baseunit 221 at predetermined intervals in a circumferential direction. Theplurality of radiation holes 227 are positioned to form a concentriccircle, and cross the radiation blades 226.

In the above-described rotor 200, the permanent magnets 210 arepositioned having a predetermined space from the stator 100. The drivingshaft 400 connected to the resin frame 220 is fixedly connected to otherconstitutional elements.

In the conventional outer rotor type brushless motor, when a currentsequentially flows to the coil 20 wound round the stator 100, the rotor200 is rotated according to interaction between the current flowing inthe coil 20 and the permanent magnet 210. The rotation force of therotor 200 is transmitted to other constitutional elements through thedriving shaft 400.

For example, in case the outer rotor type brushless motor adapts to awashing machine, the stator 100 is deposited in an outer casingincluding an inner casing, the driving shaft 400 is connected to theinner casing of the washing machine, and thus the driving force of therotor can be transmitted to the devices such as the washing machinethrough the driving shaft 400.

During the rotation of the rotor 200, the air flows into the motor bythe radiation fan blades 226 and the radiation holes 227, therebycooling the heat generated in the motor.

However, while rotated by the interaction force with the current appliedto the winding coil of the stator, as depicted in FIGS. 3a and 3b, therotor for the conventional outer rotor type brushless motor is vibratedin a shaft direction and a radius direction.

The vibration is generated because the resin frame connected with thepermanent magnet consists of the resin, and thus stiffness of thematerial is weak (approximately 15% of the steel plate). Especially, thevibration of the resin frame resulting from the vibration in the radiusdirection increases noise.

Moreover, since the frame consists of the resin, the serration unit ofthe frame connected to the driving shaft transmitting the driving forcegenerated from the rotor is easily abraded under the operationalconditions of high temperature, high torque and impact load, and thus alife span thereof is reduced.

In addition, the radiation fan blades for cooling the inside of themotor with the external air are formed in a vertical direction.Therefore, when the rotor is rotated in one direction, an amount of theair which flows into the motor and is discharged therefrom is increased.As the thermal conductivity of the resin is low, radiation is notefficient.

Furthermore, the frame consisting of the resin is very weak to a fatiguedestruction resulting from a repeated stress generated by alternation ofthe washing machine. Accordingly, the radiation hole must be formedsmall. However, the small radiation holes cannot sufficiently perform acooling operation. As a result, when the cooling operation isill-performed, a resistance of the coil is increased, motor efficiencyis reduced, a temperature of the coil is more increased, and thus thecoil may be easily damaged. Consequently, an expensive coil of highquality must be used.

The resin frame consists of the resin, and thus a price thereof isrelatively high. Also, it is necessary to separately fabricate andconnect the back yoke in order to form the magnetic circuit, whichresults in increased production and assembly costs.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea structure of a rotor for a brushless motor (BLDC) which can improvestructural stiffness, reduce noise by restricting generation ofvibration, use cheap materials, reduce a fabrication cost by forming aback yoke and a base plate unit in a single body, and improvedurability.

It is another object of the present invention to provide a structure ofa rotor for a brushless motor (BLDC) which can efficiently cool a heatgenerated in a motor during the operation by promoting inflow of anexternal air.

In order to achieve the above-described objects of the presentinvention, there is provided a structure of a rotor for an outer rotortype brushless motor (BLDC), including: a steel plate frame providedwith a base plate unit in a disc shape having a plurality of insertionholes at its center portion, a plurality of radiation holes being formedat a circumferential portion of the insertion holes, a plurality ofblades being formed at side portions of the radiation holes by cutting,a back yoke unit curved and extended in the upward direction, having apredetermined height at the circumferential portion of the base plateunit, and a radius-direction enhancing unit formed at the upper endportion of the back yoke unit; one or a plurality of ring type permanentmagnets fixedly connected to the inner side portion of the back yokeunit; a connecting member inserted into the insertion hole positioned atthe center, and connected to the steel plate frame; and a fixing unitfixing a driving shaft inserted into the connecting member and connectedto the other constitutional elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become better understood with reference tothe accompanying drawings which are given only by way of illustrationand thus are not limitative of the present invention, wherein:

FIG. 1 is a front cross-sectional view illustrating a conventional outerrotor type brushless motor (BLDC);

FIG. 2a is a front cross-sectional view illustrating a structure of arotor for the conventional outer rotor type brushless motor;

FIG. 2b is a plan view illustrating the structure of the rotor for theconventional outer rotor type brushless motor;

FIG. 3a is a front cross-sectional view illustrating a state where therotor is vibrated in a radius direction during the driving of theconventional outer rotor type brushless motor;

FIG. 3b is a front cross-sectional view illustrating a state where therotor is vibrated in a shaft direction during the driving of theconventional outer rotor type brushless motor;

FIG. 4a is a front cross-sectional view illustrating the structure ofthe rotor for the outer rotor type brushless motor in accordance withthe present invention;

FIG. 4b is a plan view illustrating the structure of the rotor for theouter rotor type brushless motor in accordance with the presentinvention;

FIG. 4c is a bottom view illustrating a structure of a rotor for anouter rotor type brushless motor in accordance with a preferredembodiment of the present invention;

FIG. 5a is a cross-sectional view illustrating an enhancing rib formedon the rotor for the outer rotor type brushless motor in accordance withthe present invention;

FIG. 5b is a cross-sectional view illustrating another embodiment ofFIG. 5a;

FIG. 6 is a bottom view illustrating another embodiment of FIG. 4C;

FIG. 7a is a cross-sectional view illustrating radiation holes andblades formed on the rotor for the outer rotor type brushless motor inaccordance with the present invention;

FIG. 7b is a cross-sectional view illustrating another embodiment ofFIG. 7a;

FIG. 8 is a front cross-sectional view schematically illustrating afirst example of a support frame connected to an outer circumferentialportion of a back yoke unit of the rotor of the outer rotor typebrushless motor in accordance with the present invention;

FIG. 9 is a front cross-sectional view schematically illustrating asecond example of the support frame in FIG. 8;

FIG. 10 is a front cross-sectional view schematically illustrating athird example of the support frame in FIG. 8; and

FIG. 11 is a front cross-sectional view schematically illustrating afourth example of the support frame of FIG. 8;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A structure of a rotor for an outer rotor type brushless motor (BLDC) inaccordance with preferred embodiments of the present invention will nowbe described with reference to the accompanying drawings.

Here, the identical constitutional elements to the conventional art areprovided with the same reference numerals.

As illustrated in FIGS. 4a to 4c, the rotor for the outer rotor typebrushless motor in accordance with the present invention includes asteel plate frame 510 in a cylinder shape having a plurality ofinsertion holes 511 at its center portion, an upper portion of whichbeing opened. A back yoke unit 513 is curved and extended in the upwarddirection, having a predetermined height at the outer circumferentialportion of a base plate unit 512, a plurality of permanent magnets 520being fixedly connected to an inner side portion of the back yoke unit513.

The base plate unit 512 is formed in a disc shape, a center portion ofwhich being protruded in the upward direction, making an irregular shapewith peripheral portions.

The plurality of insertion holes 511 are formed at the center portion,and include a shaft insertion hole 511a which a driving shaft 400 isinserted into; and a plurality of fastening member insertion holes 511bwhich are formed at the outer circumferential portion of the shaftinsertion hole 511a, and which a fastening member 520 is inserted into.

On the other hand, a connection guide unit 514 is protrusively formed inthe upward direction at the outer circumferential portion of thefastening member insertion hole 511b in the base plate unit 512, so thata connecting member 530 fastened to the steel plate frame 510 by thefastening member 520 can be easily connected to the base plate unit 512.

The connecting member 530 consists of a steel material, and is fixedlyconnected to the steel plate frame 510.

As depicted in FIGS. 4b and 4c, in order to increase a natural frequencyof the rotor 500, a plurality of enhancing ribs 515 which arelongitudinally embossed in a radius direction are formed in a radialshape at a predetermined portion of the base plate unit 512.

The enhancing ribs 515 serve to prevent generation of resonance withother constitutional elements during the driving of the rotor 500.

As illustrated in FIGS. 5a and 5b, the end portion of the enhancing rib515 is advantageously formed in an isosceles triangle shape. Theembossing direction is protruded toward the upper or lower portion ofthe base plate unit 512.

In addition, a plurality of radiation holes 516 are formed at the outercircumferential portions of the plurality of insertion holes 511 formedat the center portion of the base plate unit 512. A blade 517 forguiding an air inflow by rotation of the rotor 500 is formed at the sideportions of the respective radiation holes 516.

The radiation hole 516 and the blade 517 may be formed by a pressprocess at the same time, or the blade 517 may be adhered after formingthe radiation hole 516. One or more radiation holes 516 and blades 517are formed between the enhancing ribs 515 at predetermined intervals.

According to a preferred embodiment as shown in FIG. 4c, one radiationhole 516 and one blade 517 are formed between the enhancing ribs 515.According to another embodiment as shown in FIG. 6, two radiation holes516 and two blades 517 are formed between the enhancing ribs 515.

In general, it is preferable that the radiation holes 516 are formed ina maximum number so long as the structural stiffness of the base plateunit 512 is maintained, and thus maximizes an amount of air flowing intothe motor.

The shape of the radiation hole 516 will now be described in detail. Theradiation hole 516 is longitudinally formed in a radius direction at thebase plate unit 512. The blade 517 is fixed after an edge of a cuttingportion of the radiation hole 516 is rotated by a predetermined angle.

In more detail, as illustrated in FIGS. 7a and 7b, in order to form theradiation hole 516, a predetermined portion of the base plate unit 512is cut in the radius direction. The cutting portion is rotated by apredetermined length (h), centering around a portion corresponding to alength (L) to the circumferential direction of the radiation hole 516,and fixed, thereby forming the blade 517.

In every embodiment, it is advantageous to form the plurality of blades517 to be sloped in the same direction, and to form a width of theradiation hole 516 to be equal to or greater than a height of the blade517 (h/L≦1). In addition, the blade 517 slopes toward the inner or outerside of the stator coil 20. Here, an angle of slope is preferablybetween 60° and 90° in regard to the surface of the base plate unit 512.as shown in FIGS. 7a and 7b.

FIG. 7a shows a state where the blade 517 is fixedly sloped toward thestator coil 20, and FIG. 7b shows a state where the blade 517 is fixedlysloped away therefrom. In the former, a large amount of air flows intothe motor, but an accident may take place during components assembly. Inthe latter, an amount of air flowing into the motor is more or lesssmall, but an accident is prevented.

In order to receive one or more ring-shaped permanent magnets 540 in thecircumferential direction at predetermined intervals, a jaw 513a havinga predetermined width in a horizontal direction and a contact surface513b extended in a vertical direction to the jaw 513a are formed at theinner surface of the back yoke unit 513.

The permanent magnets 540 are positioned on the jaw 513a, contacted withthe contact surface 513b, and fixedly connected to the back yoke unit513 by an adhesive or, by positioning a resin for adhesion 550 at theirupper portions.

In order to enhance stiffness of the steel plate frame 510 in the radiusdirection, a radius-direction enhancing unit 518 vertically curved andextended in the outward direction is formed at the upper end portion ofthe back yoke unit 513.

In accordance with a second embodiment of the present invention, asshown in FIG. 8, in order to more enhance stiffness in the radiusdirection, a radius-direction enhancing unit 618 is inwardly curved atan upper portion of a region supporting the magnets 540, therebysupporting the magnets 540 by an elastic force of the base plate unit512. In addition, in order to enhance stiffness of the base plate unit512 consisting of a steel material in the radius direction, a supportframe 660 is provided at the outer portion of the base plate unit 512,and an upper end portion thereof is horizontally curved and extended inthe outward direction.

That is to say, the support frame 660 is curved several times, thuspartially surrounding the outsides of the bottom and side portions ofthe back yoke unit 613. The upper end portion thereof is outwardlycurved and extended.

On the other hand, in accordance with a third embodiment of the presentinvention, as illustrated in FIG. 9, a radius-direction enhancing unit718 is vertically curved and extended in the outward direction at theupper end portion of a back yoke unit 713, and a support frame 760 iscurved, thereby surrounding the whole outsides of the bottom and sideportions of the back yoke unit 713.

In accordance with a fourth embodiment of the present invention, asshown in FIG. 10, a radius-direction enhancing unit 818 is extendedlyformed in a reverse U shape in the outward direction at the upper endportion of the back yoke unit 813.

According to a fifth embodiment of the present invention. as depicted inFIG. 11, a radius-direction enhancing unit 918 is vertically curved andextended in the outward direction at the upper end portion of the backyoke unit 913, and a support frame 960 is formed in a disc shape withits center portion empty, as if covering the upper circumferentialportion of the steel plate frame 512, facing an inner portion thereof.

As described above, the support frame in accordance with the respectiveembodiments of the present invention is protrusively formed in theinward or outward direction of the base plate unit 512, therebysufficiently enhancing the stiffness in the radius direction.

On the other hand, the connecting member 530 includes: a ring-shapedflange unit 531 having a predetermined thickness and area; a boss unit532 upwardly extended at the center portion of the flange unit 531, andhaving a predetermined outside diameter and height; a serration hole 533formed at an inner circumferential portion of a through hole 532a formedat the boss unit 532 in upper and lower directions, and engaged with theshaft serration unit 401 formed at the driving shaft 400; and aplurality of connecting member combining units 534 formed at the flangeunit 531, and fastened to the fastening member 520.

The plurality of connecting member combining units 534 formed at theflange unit 531 are screw holes making a concentric circle shape.

A guide hole 535 which the connection guide unit 514 formed at the upperportion of the base plate unit 512 is inserted into is formed having apredetermined depth at the lower portion of the connecting membercombining unit 534.

On the other hand, although not illustrated in the drawings, a specificguide pin may be formed in the connection guide unit 514.

The fastening unit 520 includes a plurality of bolts. The bolts arepassed through the fastening unit insertion holes 511b, and thereafterfastened to the connecting member combining unit 534, thereby connectingthe connecting member 530 to the base plate unit 512 of the steel plateframe 510. A specific nut may be fastened to the fastening unit 520.

The shaft serration unit 401 is formed at the outer circumferentialportion of the driving shaft 400 transmitting the rotation force of therotor 500 in order to be engaged with the serration hole 533 of theconnecting member 530, and a male screw unit 402 is formed at the lowerportion thereof.

The driving shaft 400 is connected to the serration hole 533 of theconnecting member 530 connected to the steel plate frame 510. At thesame time, the spacer 410 is inserted into the end portion of thedriving shaft 400, and the nut 420 which is a fixing unit is fastened tothe male screw unit 402, thereby fixedly connecting the driving shaft400 to the steel plate frame 510.

The assembly process of the rotor for the outer rotor type brushlessmotor in accordance with the present invention will now be explained.

Firstly, the shape of the steel plate frame 510 is manufactured by apress. The permanent magnets 540 are positioned at the innercircumferential portion of the back yoke unit 513 of the steel plateframe 510. Thereafter. the permanent magnets 540 are fixedly adhered tothe back yoke unit 513 by the adhesive or resin for adhesion 550.

The screw hole 534 which is the connecting member combining unit accordswith the fastening unit insertion hole 511b of the base plate unit 512of the steel plate unit 510, and a bolt which is the fastening unit 520is fastened thereto, thereby connecting the connecting member 530 to thesteel plate frame 510.

The shaft serration unit 401 of the driving shaft 400 is inserted intothe serration hole 533 of the connecting member 530, the spacer 401 isinserted into the lower portion of the driving shaft 400, and the nut420 is fastened to the male screw unit 402 of the driving shaft 400,thereby fixedly connecting the driving shaft 400, the steel plate frame510 and the connecting member 530.

In accordance with the outer rotor type brushless motor of the presentinvention, the permanent magnets 540 composing the rotor 500 arepositioned to surround the stator 100, and the driving shaft 400 isconnected to other constitutional elements.

According to the outer rotor type brushless motor of the presentinvention, when a current is applied to the coil 20 composing the stator100, the rotor 500 is rotated by the interaction force between thecurrent flowing in the coil 20 and the permanent magnets 540, and thedriving shaft 400 connected to the rotor 500 transmits the rotationforce generated from the rotor 500 to the other constitutional elements.

In accordance with the present invention, the steel plate frame 510consists of a steel material, and thus stiffness is relatively high. Inaddition, at the base plate unit of the steel plate frame 510, theenhancing rib 515 is formed in order to enhance stiffness in the shaftdirection, and the radius-direction enhancing unit 518 if formed inorder to enhance stiffness in the radius direction. The support frame isconnected to the outer portion of the enhancing unit 518, thusincreasing the structural stiffness and reducing the vibration. As aresult, the noise generation is restricted.

Also, the blades 517 formed at the base plate unit 512 of the steelplate frame 510 are protrusively sloped in one direction, and thus theexternal air may smoothly flow into the motor during the rotation.Accordingly, the heat generated in the motor can be efficiently cooled.

Furthermore, the connecting member 530 connected to the driving shaft400 is firmly fastened to the steel plate frame 510 by the bolt which isthe fastening unit 520. Also, the material stiffness is high, and thusresists the high torque, impact load and high temperature. As a result,the components may not be abraded or damaged, and durability thereof isimproved.

Moreover, the steel plate frame 510 and other components consist of asteel material, and thus a fabrication cost thereof is reduced byapproximately 5 times, as compared with the resin in the conventionalart. In addition, while the back yoke 230 is fabricated by rolling athin steel plate in the conventional air, it is not speciallyfabricated, but formed in a single body with the steel plate frame 510in accordance with the present invention.

As discussed earlier, the structure of the rotor for the outer rotortype brushless motor in accordance with the present invention increasesthe structural stiffness, and restricts generation of the vibration andnose during the operation, thereby improving reliability. In addition,the present invention efficiently cools the heat generated in the motorduring the operation, thereby improving the efficiency of the motor.Moreover, the back yoke unit is not specially fabricated, but formed ina single body with the steel plate frame, thereby reducing thefabrication cost.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof it shouldalso be understood that the above-described embodiments are not limitedby any of the details of the foregoing description, unless otherwisespecified, but rather should be construed broadly within its spirit andscope as defined in the appended claims, and therefore all changes andmodifications that fall within the meets and bounds of the claims, orequivalences of such meets and bounds are therefore intended to beembraced by the appended claims.

1. A structure of rotor for an outer rotor type brushless motor,comprising: a steel plate frame including: a base plate unit in a discshape having: a plurality of insertion holes at its center portion; aplurality of radiation holes being formed at a circumferential portionof the insertion holes; a plurality of radially extending blades beingformed at side portions of the radiation holes by cutting; a connectionguide unit being protrusively formed adjacent a circumferential portionof a shaft insertion hole of the plurality of insertion holes; aplurality of enhancing ribs which are longitudinally embossed in aradial direction formed in intermediate between a center and an outeredge thereof; a back yoke unit curved at the edge portion of the baseplate unit and formed integrally therewith and extended in the upwarddirection, having a predetermined height at an outer circumferentialportion of the base plate unit; and a radius-direction enhancing unitformed radially extending outwardly at an upper end portion of the backyoke unit; one or a plurality of ring type permanent magnets fixedlyconnected to the inner side portion of the back yoke unit; a connectingmember inserted into the shaft insertion hole of the plurality ofinsertion holes positioned at the center, and connected to the steelplate frame by a fastening member; and a fixing unit fixing a drivingshaft inserted into the connecting member which connected to the otherconstitution elements.
 2. The structure according to claim 1, wherein ajaw having a predetermined width in a horizontal direction and a contactsurface extended in a vertical direction to the jaw are formed at aninner surface of the back yoke unit.
 3. The structure according to claim2, wherein the permanent magnets are positioned on the jaw, contactedwith the contact surface, and fixedly connected to the back yoke unit byan adhesive or by positioning a resin for adhesion at their upperportions.
 4. The structure according to claim 1, wherein the pluralityof insertion holes are formed at the center portion of the base plateunit, and comprise the shaft insertion hole which the driving shaft isinserted into, and a plurality of fastening member insertion holes whichare formed at the outer circumferential portion of the shaft insertionhole, and a fastening member is inserted into.
 5. The structureaccording to claim 4, wherein a connection guide unit is protrusivelyformed in the upward direction at the outer circumferential portion ofthe fastening member insertion hole.
 6. The structure according to claim1, wherein the connecting member comprises: a ring-shaped flange unithaving a predetermined thickness and area; a boss unit upwardly extendedat the center portion of the flange unit, and having a predeterminedoutside diameter and height; a serration hole formed at an innercircumferential portion of a through hole formed at the boss unit inupper and lower directions, and engaged with a shaft serration unitformed at the driving shaft; and a plurality of connecting membercombining units formed at the flange unit and fastened to the fasteningmember.
 7. The structure according to claim 6, wherein a guide holewhich the connection guide unit protrusively formed at adjacent acircumferential portion of a shaft insertion hole of the plurality ofinsertion holes which inserted into is reamed having a predetermineddepth at the lower portion of the connecting member combining unit. 8.The structure according to claim 1, wherein a cross-section of theenhancing ribs is symmetric in the radius direction.
 9. The structureaccording to claim 1, wherein an embossing direction of the enhancingribs is protruded inwardly toward a stator coil.
 10. The structureaccording to claim 1, wherein an embossing direction of the enhancingribs is protruded outwardly away from where a stator coil is located.11. The structure according to claim 1, wherein a plurality of enhancingribs embossed and longitudinally formed in a radial shape are formed inthe radius direction at a predetermined portion of the base plate unit,and one or more radiation holes and blades are formed between theenhancing ribs.
 12. The structure according to claim 1, wherein theplurality of radiation holes are longitudinally formed in the radiusdirection of the base plate unit.
 13. The structure according to claim12, wherein a width of the radiation holes is equal to or greater than aheight of the blades.
 14. The structure according to claim 1, whereinthe respective blades are sloped inwardly or outwardly toward or awayfrom a stator coil.
 15. The structure according to claim 14, wherein aslope angle of each of the blades is between 85° and 95° relative to thesurface of the base plate unit.
 16. The structure according to claim 1,wherein the radius-direction enhancing unit is vertically curved andextended in the outward direction at the upper end portion of the backyoke unit.
 17. The structure according to claim 1, wherein theradius-direction enhancing unit is extendedly formed in a reverse Ushape in the outward direction at the upper end portion of the back yokeunit.
 18. The structure according to claim 1, wherein a support frame isconnected to the outer portion of the back yoke unit.
 19. The structureaccording to claim 18, wherein a radius-direction enhancing unit isinwardly curved and extended at the upper portion of the back yoke unit,and thus the permanent magnets are supported by an elastic force of theback yoke unit itself.
 20. The structure according to claim 18, whereinthe support frame is curved several times, and thus partially surroundsthe outsides of the bottom and side portions of the back yoke unit. 21.The structure according to claim 18, wherein a radius-directionenhancing unit is vertically curved and extended in the outwarddirection at the upper end portion of the back yoke unit, and thesupport frame is curved, and thus surrounds the whole outsides of thebottom and side portions of the back yoke unit.
 22. The structureaccording to claim 18, wherein the radius-direction enhancing unit isvertically curved and extended in the outward direction at the upper endportion of the back yoke unit, and the support frame is formed in a discshape with its center portion empty, as if covering the uppercircumferential portion of the steel plate frame, facing an innerportion thereof.
 23. A rotor for an outer rotor type brushless motor fora washing machine, comprising: a steel plate frame including: a baseplate unit in a disc shape having: a plurality of insertion holes at itscenter portion; a plurality of radiation holes formed at acircumferential portion of the insertion holes; a plurality of radiallyextending blades formed at side portions of the radiation holes; aconnection guide unit protrusively formed adjacent a circumferentialportion of a shaft insertion hole of the plurality of insertion holes; aplurality of enhancing ribs which are longitudinally embossed in aradial direction formed intermediate a center and an outer edge thereof;a back yoke unit curved at the edge portion of the base plate unit andformed integrally therewith and extended in an upward direction, havinga predetermined height at an outer circumferential portion of the baseplate unit; and a radius-direction enhancing unit formed radiallyextending outwardly at an upper end portion of the back yoke unit; atleast one ring type permanent magnet fixedly connected to the inner sideportion of the back yoke unit; a connecting member inserted into theshaft insertion hole of the plurality of insertion holes positioned atthe center, and connected to the steel plate frame by a fasteningmember; and a fixing unit fixing a driving shaft inserted into theconnecting member which is connected to the other elements of thewashing machine.